The use of holographic techniques, in particular kinoforms (phase only holograms) in telecommunications presents special problems, in particular because of the high signal-to-noise (SNR)/low crosstalk requirements as compared with display applications. For example in a display application the level of noise/crosstalk may be of order 1:300 whereas in a telecommunications device it may be of order 1:10000. other special problems which can arise are as follows:                Operation at the long wavelength of 1.5 micron necessitates the use of thick liquid layers (compared with visible light devices), making the accurate rendition of the pixel array pattern in the liquid crystal more difficult.        High diffraction efficiency and very low crosstalk are required.        Reconfigurable dynamic pixilated kinoforms rendered on LCOS devices have special problems compared with fixed kinoforms produced by photolithographic processes. They have a relatively large pixel size and the size of the pixel array is limited and they suffer from artefacts related to the liquid crystal layer.        In some cases relatively fast computation of pixel patterns is required e.g. to adaptively adjust beams or the configure new switch configurations.        
Background prior art can be found in U.S. Pat. No. 5,617,227; U.S. Pat. No. 5,416,616; WO03/021341; U.S. Pat. No. 7,457,547; and “Iterative algorithm for the design of diffractive phase elements for laser beam shaping”, J. S. Liu and M. R. Taghizadeh, Aug. 15, 2002, Vol. 27, No. 16, OPTICS LETTERS p. 1463; “Hologram Optimisation Using Liquid Crystal Modelling”, Georgiou A. G. et al., Molecular Crystals and Liquid Crystals 2005 vol 434 pp 511-526; and “Fresnel ping-pong algorithm for two-plane computer-generated hologram display” in 10 Feb. 1994/Vol. 33, No. 5/APPLIED OPTICS pp. 869).